Hi,
Noted your short and specific history of some bite on hand that took 1 week to settle but now development of welt along waist line that settled on its own, occurs on sitting for a long time.
The history is specific about some bite on hand that caused swelling and it seems that you have not taken any treatment.
Thus the obvious cause looks to be an
allergic reaction caused by some bite that is still circulating in blood and causing
angioneurotic edema along the waistline.
The additional cause can be the elastic in the underwear that when reacted with the sweat can cause similar reaction.
I would advise you the following in such a situation:
First of all take an antihistamine like
Cetirizine and see if this settled.
If antihistamine alone is not sufficient means you will need oral
steroid and needs a valid prescription of your Doctor hence consult your Doctor.
Take steroid in tapering doses.
Watch for
diabetes.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, General Surgeon